Iron casting



Feb. 27, 1945. R. L. WILSON v 2,370,279

IRON CASTING Filed July 9, 1945 JFZ #nfar;

R0656) Z. M16072 Patented Feb. 27, 1945 IRON CASTING i Rosser L.Wilson,'Mahwah, N. J., assignor to American Brake Shoe Company,Wilmington,

Del., a corporation of Delaware Application July 9, 1943, Serial No.493,958

4 Claims.

This invention relates to iron castings, such as the brake shoes used onrailway and like equipment, and to the production thereof.

The brake shoes that are used on railway and like equipment are examplesof iron castings 1 which may be produced in different degrees ofhardness and in which it is usually desired to insure at least apredetermined degree of hardness. Thus, to refer to specific examples ofbrake shoes desirably having different degrees of hardness, those brakeshoes whichare used on equipment operated on elevated and subway linesin metropolitan areas, which equipment is decelerated at rather frequentintervals, are usually relatively hard so as to reduce the rate of Wearthereof, whereas those'brake shoes which are employed on mine or ore orother relatively heavily loaded cars, which are often operated onrelatively steep inclines, are usually comparatively soft so as toembody relatively high frictional characteristics. The foregoingreference to specific types of kinds of brake shoes is merely exemplarysince there are many other instances where brake shoes of varyingdegrees. of hardness are advantageously employed. Moreover, to insureagainst an excessive rate of wear and in a measure to control thefrictional-'characteristics, the degree of hardness of many brake shoesis desirably maintained above a predetermined minimum.

Brake shoes of the character to'which this invention pertains are cast'inmolds that are set out on a foundry floor. In modern foundrypractice, the molds which are set out on the floors for pouring areoften produced in' such a manner that molds for several difierenttypesof castings may be more or less indiscriminately distributed throughouta floor. This is particularly true in those instances where moldsareproduced at intervals along a conveyor which isv effective to carrythe molds from the point of production to the floor upon which the moldsare set out. Thus, for example, a mold for a particular'castring may beproducedat a particular pointalong :the'conveyor while, a mold for -adifferent casting may be produced at another point along the conveyorand as the molds so produced are placed upon the carrier, molds fordifferent castings collect one after the other along the conveyor. Whenmolds so produced are picked up from the conveyor and are then set outon a floor, a more or less indiscriminate'distribution of molds fordifferent castings on-the floor results. Hence, it may well be thatmolds, for brake shoes or other castings in which a relatively highdegree of hardness is desired will be distributed on-afloor among moldsfor-brake shoes or other castings which are to be relatively-soft.Moreover, molds for relatively large and heavy shoes or other castingsmaybe distributed among molds for comparatively small and light shoes orother castings. It is, however, highly desirable in such instances thatadjacent molds on a floor be poured from the same ladle. Thus where, forexample, molds for large and small shoes, or molds'for brake shoes thatareto be comparatively hard arev dis-'- tributed among molds for shoesthat areto be comparativelyisoft, it is quite difficult to-so'controlthe iron that the -proper degree of hardness desired in the variousshoes may be realized-when the molds are poured from the same ladle and,in the alternative, resort must'b'e had to pouring the molds fromdifferent ladles which mate rially and objectionably increasesmanufacturing costs. 9

It is known, however, that iron castings of varying'degrees of hardnessmay be produced by varyin the chill effect to which the iron issubjected in a mold and where relatively hard castings aredesire'djthis' maybe realized by effectively and-quickly chillingthehot; iron in the mold. It is comparatively easy to produce arelatively high chill effect byincorporating what are known as chillblocks into amold but so to do produces a "relatively hard surface'onthe castings, and brake shoes, such as are used on railway and likeequipment, are examples of instances where chilled surface areasaredesired only at determined or selected positions; Such shoes are,therefore, exemplary of," instances where resort cannot behadsa'tisfactorily to chill blocks in orderto selectively producecastingsof varying degrees 'ofhardness in instances'where the molteniron is poured-from the same ladle into molds for shoes of varyingdesired characteristics and configurations. v

- In this respect,' however, brake shoes such as are used on railwa andlike equipment .are also exemplary of iron castingsin whichreinforcements are-usually included: Thus it is customary 1 toincorporate an insert in a brake shoe and such an insert usuallyconsists of a plurality of layers of expanded metal. Such inserts, priorto the time they are incorporated into a mold, are usually coated with arefractory material so asto prevent objectionable burning thereof as themolten iron flows thereabout in thecasting operation. Suoha-refractorycoating has the effect of chillingtheironythat flows into contacttherewith but such eifect is so limited as to be negligible for allpractical purposes.

There are, however, certain substances which exhibit a marked chillingeffect upon hot iron and among such substances is tellurium which actsas a powerful iron carbide stabilizer, which is to say, a relativelysmall amount of tellurium is effective vto keep whatever carbon may bepresent in the form of iron carbide during the pouring andsolidification of cast iron. Therefore, in an instance where it isdesired to provide iron castings of varying degrees of hardness and particularly where it is desirable or advantageous that the molten iron bepoured from a common ladle into the molds in which the castings are tobe produced, I propose to incorporate in at least selected of the moldsvarying quantities of a substance, such as tellurium, to controlth'edegree of hardness in the resulting castings and so to do is the primaryobject of the present invention.

Moreover, in those instances where the castings are to include areinforcement which is coated with a refractory material prior to incorporation thereof in the mold,'I propose to incorporate into therefractory coating that quantity of a substance, such as tellurium, thatwill produce the desired degree of hardness in the resulting castingwith reference, of course, to the chill eifect of the molten iron. Thus,for example, where castings of 'varying degrees of hardness are to beproduced in molds into which molten iron will be introduced from acommon ladle, I so control the molten iron that those castings which areto be comparatively soft will be produced when the molten iron does notcome into association with a substance such as tellurium in a particularmold and then by incorporating various quantities of a substance such astellurium in at least selected of the other molds, I am enabled toproduce castings of various degrees of hardnessin molds into which ironis poured from the ladle, the greatest quantity of a substance such astellurium being included in the mold in which the casting of thegreatest degree of hardness is to be produced and to enable theforegoing to be realized in a novel and efllcient manner is yet anotherimportant object of this invention.

It is particularly advantageous to include a substance such astelluriumin the refractory coating provided about an insert which is to beembedded or enclosed in an iron casting for so to do enables thegreatest degree of hardness to be produced in the casting immediatelyabout the insert included therein or, in other words, interiorly of thecasting whereby, in effect, the softer iron will tend to enclose andsurround the chilled and harder iron 50 as to thereby protect the same.This is particularly important in a casting, such as a brake shoe, whichis to be subjected to thermal shock. Thus, for example, when the wearingface of a brake shoe is applied to the periphery of a rotatirigelementto eflect deceleration thereof, the wearing face of the shoe is rapidlyheated to a comparatively high temperature while the remainder of theshoe may remain comparatively cool and this, of course, subjects thebrake shoe to a severe ther-- mal shock. However, where a brake shoeembodies a hard or white iron portion that is enclosed within a mottledor grey iron portion, very effective resistance to thermal shock isaflorded and to enable this advantageous result to be realized is yetanother object of this invention.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawing which, by way of illustration, shows a preferredembodiment and the principle thereof and what I now consider to be thebest mode in which I have contemplated applying that principle. Otherembodiments of the invention embodying the same or equivalent principlemay be used and structural changes may be made as desired by thoseskilled in the art without departing from the present invention and thepurview of the appended claims.

In the drawing,

Fig. l is a side view, partly in elevation and partly in section, of atypical brake shoe embodying my invention; and

Fig. 2 is a transverse sectional view taken sub stantially on the line2-2 on Fig. l.

The brake shoe shown in the accompanying drawing is of the characteradapted for use with the wheel of a railway car or the like but it willbe understood that my invention may be embodied in a brake shoe adaptedfor use with the driver wheel of a locomotive or in any other casting inwhich it will be advantageous to have a hard iron portion enclosedwithin mottled or grey iron or in which casting it is desired to controlthe degree of hardness. The brake shoe illustrated in the accompanyingdrawing includes a cast iron body'B in which a reenforcement EM isembedded, the illustrated reenforcement comprising a plurality of layersof expanded sheet metal. Moreover, a ductile metal reenforce SB,commonly referred to as a steel back, is provided at the back of theshoe. End stops E integral with the body B are provided on the back andat the ends of the shoe and a center attaching lug L is also provided onthe back of the shoe midway between the ends thereof, the foregoingarrangement of a brake shoe being in accordance with well-understoodpractices.

Moreover, as is customary in the art, at least a part of the steelbacking SB and the reenforcement EM are coated with a refractorymaterial prior to the time they are introduced into a mold, and molteniron is poured thereabout to afford the body B of the shoe, for so to doprotects such reenforcements against burning when the molten metal flowsthereabout in the mold. A suitable refractory coating for reenforcementsas SB and EM that has been used heretofore consists of silica flour, acarrier such as linseed oil and a thinner such as naphtha all intermixedin such proportions as to afford what may well b called a paint andusually the proportions are such that the paint has a specific gravityof from about 1.3 to about 1.4. The reenforcements are usually dippedinto such a paint and are there'- after permitted to dry prior to beingintroduced into. a mold in which a brake shoe is to be cast.

Of course any refractory material that is included in a mold willhavesome chilling effect on molten iron that flows into contact therewith,but it has beenobserved that the chilling eifect of the refractorycoatings that are included on reenforcements, such as those which arereferred to hereinabove, is such that hardly more than a traceof hard orwhite iron will be found in a casting in which reenforcements so coatedprior to the casting operation are embedded and therefore the presenceof a refractory coating such as that described hereinabove does notenable the novel and advantageous results of the present invention to berealized inasmuch as, in

accordance with this inventiom usually a substantial portion of thecasting is to be compara tively hard as by being converted to whiteiron.

However, a relatively deep chill in the iron may be obtained byincluding in a refactory coating, such as that described hereinabove, amaterial that is effective to bring about chilling of the iron. Onematerial which possesses this property to a marked degree is telluriumfor the reason that tellurium acts as a powerful iron carbidestabilizer, which is to say, a small amount of tellurium is effective tokeep the carbon in the form of iron carbide during the pouring andsolidification of chilled cast iron. Therefore, in accordance with thepresent invention from about one-quarter ounce to about two ounces oftellurium is added to one pound of a paint of the aforesaid characterfor it has been found that so to do will airord from approximately .001pound to about .005 pound of tellurium in a standard railway passengercar brake shoe including an expanded metal insert consisting of sevenlayers of expanded sheet metal as, for example, expanded eighteen gaugerolled sheet steel and approximately twenty-three pounds of cast ironalong with a ductile metal reenforcing back weighing approximately onepound. This affords, in relation to the weight of the brake shoe,approximately .005% of tellurium in the shoe, and this enables the noveland advantageous results of the present invention to be realized.

Thus, when a metallic insert such as the reenforcement EM is dipped intoa paint of the aforesaid character including tellurium in the quantityspecified above and in the conventional placed in a mold in which abrake shoe is to be cast in the conventional manner from a chillingiron, a white iron core enclosed within a mottled or grey iron shell mabe afforded since such amounts of tellurium will be effective to keepthe carbon in the form of iron carbide during the pouring andsolidification of an appreciable portion of the cast iron in the regionabout the coated insert. Moreover, in those instances where tellurium ispresent in the preferred proportions, such as those specifiedhereinabove, the chilling effect thereof will usually not be sufficientto chill the iron adjacent to the exterior surfaces of the shoe so thattherefore a White iron core or center portion is afforded that isintegral with and surrounded by a mottled or grey iron enclosure orshell, such a center portion being indicated by the dotted portion inFigs. 1 .and 2.

It will therefore be appreciated that in accordance with the practice ofthis invention tellurium is introduced into a mold in such a way thatthe iron carbide stabilizing effect thereof will be effective to affordthe inner or core portion in a casting, such as a brake shoe, but desireably thequantity of tellurium that is thus utilized is so related to thesize of the casting that the iron carbide stabilizing efiect thereofwill be confined to the portion of the iron immediately thereabout sothat an integral mottled or grey iron shell or enclosure will beafforded about that portion of the iron in which iron carbide isretained during the pouring and solidification of the cast iron.However, while the inclusion of minute quantities of tellurium in apaint into which a reenforce that is to be embedded in the casting is tobe dipped i a convenient way of introducing tellurium into a mold sothat the aforesaid resultsmay be realized, it will be understood thatresort'may be had to other: ways of introducing the tellurium into themold without departing from the ambit of the present invention.

As is well understood, many castings of which brake shoes are exemplarycustomarily embody chilled portions. For example, it is customary tochill the end portions of a brake shoe adjacent to the wearing facethereof and this is realized by including What are customarily calledchill blocks in the mold so that when the molten cast iron flows intothe mold such blocks will be effective to bring about chilling of theiron in that portion of the casting that is formed immediately adjacentto such chill blocks. It is within the purview of my invention to permitthe use of chill blocks and the like in connection with the castingsembodying the present invention so that while in the main castingsembodying this invention will include a core of hard or white ironintegral with and enclosed within a shell of mottled or grey iron, it isnot essential that all portions of the shell or enclosure be of greyiron. In those instances, however, where por I tions of the enclosure orshell are to be converted to hard or white iron, it is desirable, inaccordance with the practice of my invention, that this be brought aboutother than by relying upon the effect of the tellurium that is toproduce the hard or white iron core. Thus it is desirable. in thepractice of this invention, if portions of the mottled or grey ironenclosure are to be converted to white iron, that thisbe realized byutilizing chill blocks or other well-understoodv means to bring aboutthe chilling of the desired portions of the enclosure or shell,

Moreover, resort may be had to my invention in those instances where itis desired to insure that castings such as brake shoes will embody atleast a minimum degree ofhardness. In such circumstances a smallquantity of tellurium may be included in the coating applied to insertsto be included in the castings and in such circum"- stances the molteniron will be arranged so that those castings which are poured in moldsin which no tellurium is included will be softer than the desiredminimum degree of hardness. In such circumstances, however, those moldsin which tellurium is included will produce castings embodying at leastthe minimum degree of hardness for the quantity of tellurium included insuch molds will be such, with reference to the chilling effect of theiron, as to insure that at least the desired minimum degree of hardnesswill be afforded in the castings. Another circumstance in which resortmay advantageously be had to my invention is where the castings to beproduced in molds set out on a particular foundry floor vary in size andconfiguration or where, for example, the castings are to have varyingdegrees of hardness. In such circumstances the molten iron will be ofsuch.

nature that, for example, when it" is poured into molds in whichcomparatively smallcastings; are

to be produced or into molds in which compara tively soft castings areto be produced, such castings will be afforded when the molds do nothave tellurium included therein. In such circumstances, however,tellurium will be included in ed in the molds in which comparativelylarge and complicated castings are to be produced or in which castingsdesirably having a high degree of hardness are to be produced. In uchcircumstances all of the molds set out on a particular floor may bepoured out from a common ladle and yet the desired degree of hardnesswill be realized in all of the castings.

Hereinabove I have explained that where tellurium is included in thecoating that is to be provided about an insert that is to be enclosed ina casting, the quantity of tellurium may be so regulated that thechilling effect thereof will be confined to the iron that is solidifiedimmediately about the insert. In some circumstances, however, it may bedesirable that the chilling effect of the tellurium be realizedthroughout the area of the casting and this may be accomplished byincludingsuch a quantity of tellurium in the coating about the insertthat this result may be realized. 4

However, in those instances where the castings produced in accordancewith my invention are. to be subjected to thermal shock as are brakeshoes which are applied to a rotating element to effect decelerationthereof, it will be advantageous to so regulate the quantity oftellurium introduced into the mold in which the shoe is produced thatthe chilling effect of the tellurium wil be realized only in the ironthat solidifies immediately about the insert or the like with which thetellurium is associated. Resort to such a practice will enable arelatively hard or white iron portion to be cast integrally with andenclosed within a mottled or grey iron portion and it is by reason ofthe provision of this mottled or grey iron portion that castings Iembodying my invention are enabled to effectively withstand thermalshock. Thus it is wellknown that mottled and particularly grey ironwithstand thermal shock to a much greater deree than does hard or whiteiron. Hence, in the case of a brake shoe where the arcuate wearing facethereof is frequently subjected to a relatively rapid rise intemperature and the remainder of the shoe does not have this effectimpressed thereon, the provision of 9, mottled or grey iron portion willinsure against damage to the shoe when it is subjected to thermal shock.

Furthermore, in those instances where it is desired to pour all themolds set out on a particular floor from a common ladle and varyingdegrees of hardness are to be afforded in the castings produced in suchmolds and such castings are to have a coated insert included therein, itwill be advantageous to include different degrees of tellurium in thecoatings applied to the various inserts for, as explained hereinabove,it is this that enables varying degrees of hardness to be afforded incastings produced in molds poured from a common ladle. In suchcircumstances, the paints or coatings into Which the inserts are to bedipped, as explained hereinabove, will include varying quantities oftellurium and in order to insure that the proper inserts will be placedin the proper molds it Lal may be advantageous to color the paints orcoatings so that the. inserts dipped thereinto will be of differentcolors. Thus, for example, the coating in which the greatest quantity oftellurium is included may be colored red while the paint in which thesmallest quantity of tellurium is included may be colored green. Thiswill enable prompt identification of the inserts which will producevarying degrees of hardness in the castings and will mitigate againstthe likelihood that an improper insert will be included in a particularmold.

Hereinabove I have set forth the preferred aspects of my invention andwhile I have illustrated and described a selected embodiment of myinvention, it is to be understood that this is capable of variation andmodification and I therefore do not wish to be limited to the precisedetails set forth but desire to avail myself of such changes andalterations as fall within the purview of the following claims.

I claim:

1. A cast iron brake shoe comprising a relatively-hard white iron corehaving a metallic reenforcing insert embedded therein, said relativelyhard white iron core comprising iron in the form of carbide stabilizedin that form by means of tellurium and being encased byand beingintegral with a body of relatively soft and thermal shock resistantmottled gray iron including a portion providing a braking surface.

2 The method of making a cast iron brake shoe of the type which includesa body of cast iron having an expanded metal insert embedded thereinwhich comprises coating said expanded metal insert with a surfacecoating containing tellurium and then casting ferrous metal about thethus coated expanded metal insert thereby forming a brake shoe which hasa core of chilled relatively hard White iron in which the expanded metalinsert is embedded and which has a shell of relatively soft gray iron,highly resistant to thermal shock, surrounding said relatively hardwhite iron core and including a portion providing a Wearing face.

3. The method defined in claim 2 in which said surface coating containsrefractory material and an oil vehicle and is allowed to dry upon theexpanded metal insert before the ferrous metal is poured therearound.

4. A cast iron brake shoe, an expanded metal insert coated with arefractory surface coating containing tellurium, and a body of ferrousmetal cast about said coated expanded metal insert to form a brake shoehaving a core chilled by the tellurium of said coating toaffordrelatively hard white iron in which the expanded metal insert isembedded and which brake shoe has a shell of relatively soft gray iron,highly resistant to thermal shock, surrounding said relatively hardwhite iron core and including a portion providing a,wearing face.

. ROSSER L. WILSON.

